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Pseudosuccinea columella is a freshwater snail from the family Lymnaeidae and it is native to Americas. It is also well known species in Europe as a “hothouse alien”. It is inadvertently spreading in aquaria and in ponds within greenhouses. Unfortunately it has been found also in the wild in Europe.

The shell of Pseudosuccinea columella resembles a shell of a Succinea land snail. The height of the shell of this specimen is 10.5 mm.

It can float on the water.

As all other Lymnaeidae it has its eyes at the base of its non-retractile tentacles.

And as all other Lymnaeidae it is exchanging gas trough a breathing pore (pneumostome). Pseudosuccinea columella can slide up its tube like pneumostome like this:

Arion rufus (Linnaeus, 1758) is a large species of slug. It has an interesting defensive behiour: when irritated it can contract to hemispehrical shape.

Some authors consider Arion rufus as a subspecies of Arion ater (Linnaeus, 1758) or as the same species as Arion ater. Arion ater has the same defensive behaviour. Other Arion species can contact their body a little, but they can not contract their body so much. If you are unsure in determination, you can distinguish Arion rufus from Arion vulgaris (Moquin–Tandon, 1855) according to this defensive behaviour.

Planorbarius corneus (Linnaeus, 1758) is a freshwater snail from the family Planorbidae. All Planorbidae have hemoglobin in its respiratory system – in its blood. It is the same respiratory protein that transport oxygen in human’s blood. Albino specimen are quite popular in aquaria, but albinos occur in nature sometimes too. When a planorbid snail is an albino snail, then the color of its hemoglobin is clearly visible and the whole snail is in bright red color.

Photo of albino Planorbarius corneus on human hand:

References:

Baker F. C. 1945: The molluscan family Planorbidae. The University of Illinois Press, Urbana. page 13.